﻿<!DOCTYPE html>
<html>
<head>
  <title>Drag and Drop Example</title>
  <!-- Copyright 1998-2020 by Northwoods Software Corporation. -->
  <meta name="description" content="Use HTML5 drag-and-drop to implement dragging HTML elements onto a GoJS Diagram to create new nodes." />
  <meta name="viewport" content="width=device-width, initial-scale=1">

  <style>
    .draggable {
      font: bold 16px sans-serif;
      width: 140px;
      height: 20px;
      text-align: center;
      background: white;
      cursor: move;
      margin-top: 20px;
    }

    .palettezone {
      width: 160px;
      height: 400px;
      background: lightblue;
      padding: 10px;
      padding-top: 1px;
      float: left;
    }
  </style>
  <script src="../release/go.js"></script>
  <script src="../assets/js/goSamples.js"></script>  <!-- this is only for the GoJS Samples framework -->
  <script id="code">
    function init() {
      if (window.goSamples) goSamples();  // init for these samples -- you don't need to call this

      // *********************************************************
      // First, set up the infrastructure to do HTML drag-and-drop
      // *********************************************************

      var dragged = null; // A reference to the element currently being dragged

      // highlight stationary nodes during an external drag-and-drop into a Diagram
      function highlight(node) {  // may be null
        var oldskips = myDiagram.skipsUndoManager;
        myDiagram.skipsUndoManager = true;
        myDiagram.startTransaction("highlight");
        if (node !== null) {
          myDiagram.highlight(node);
        } else {
          myDiagram.clearHighlighteds();
        }
        myDiagram.commitTransaction("highlight");
        myDiagram.skipsUndoManager = oldskips;
      }

      // This event should only fire on the drag targets.
      // Instead of finding every drag target,
      // we can add the event to the document and disregard
      // all elements that are not of class "draggable"
      document.addEventListener("dragstart", function(event) {
        if (event.target.className !== "draggable") return;
        // Some data must be set to allow drag
        event.dataTransfer.setData("text", event.target.textContent);

        // store a reference to the dragged element and the offset of the mouse from the center of the element
        dragged = event.target;
        dragged.offsetX = event.offsetX - dragged.clientWidth / 2;
        dragged.offsetY = event.offsetY - dragged.clientHeight / 2;
        // Objects during drag will have a red border
        event.target.style.border = "2px solid red";
      }, false);

      // This event resets styles after a drag has completed (successfully or not)
      document.addEventListener("dragend", function(event) {
        // reset the border of the dragged element
        dragged.style.border = "";
        highlight(null);
      }, false);

      // Next, events intended for the drop target - the Diagram div

      var div = document.getElementById("myDiagramDiv");
      div.addEventListener("dragenter", function(event) {
        // Here you could also set effects on the Diagram,
        // such as changing the background color to indicate an acceptable drop zone

        // Requirement in some browsers, such as Internet Explorer
        event.preventDefault();
      }, false);

      div.addEventListener("dragover", function(event) {
        // We call preventDefault to allow a drop
        // But on divs that already contain an element,
        // we want to disallow dropping

        if (this === myDiagram.div) {
          var can = event.target;
          var pixelratio = window.PIXELRATIO;

          // if the target is not the canvas, we may have trouble, so just quit:
          if (!(can instanceof HTMLCanvasElement)) return;

          var bbox = can.getBoundingClientRect();
          var bbw = bbox.width;
          if (bbw === 0) bbw = 0.001;
          var bbh = bbox.height;
          if (bbh === 0) bbh = 0.001;
          var mx = event.clientX - bbox.left * ((can.width / pixelratio) / bbw);
          var my = event.clientY - bbox.top * ((can.height / pixelratio) / bbh);
          var point = myDiagram.transformViewToDoc(new go.Point(mx, my));
          var curnode = myDiagram.findPartAt(point, true);
          if (curnode instanceof go.Node) {
            highlight(curnode);
          } else {
            highlight(null);
          }
        }

        if (event.target.className === "dropzone") {
          // Disallow a drop by returning before a call to preventDefault:
          return;
        }

        // Allow a drop on everything else
        event.preventDefault();
      }, false);

      div.addEventListener("dragleave", function(event) {
        // reset background of potential drop target
        if (event.target.className == "dropzone") {
          event.target.style.background = "";
        }
        highlight(null);
      }, false);

      // handle the user option for removing dragged items from the Palette
      var remove = document.getElementById('remove');

      div.addEventListener("drop", function(event) {
        // prevent default action
        // (open as link for some elements in some browsers)
        event.preventDefault();

        // Dragging onto a Diagram
        if (this === myDiagram.div) {
          var can = event.target;
          var pixelratio = window.PIXELRATIO;

          // if the target is not the canvas, we may have trouble, so just quit:
          if (!(can instanceof HTMLCanvasElement)) return;

          var bbox = can.getBoundingClientRect();
          var bbw = bbox.width;
          if (bbw === 0) bbw = 0.001;
          var bbh = bbox.height;
          if (bbh === 0) bbh = 0.001;
          var mx = event.clientX - bbox.left * ((can.width / pixelratio) / bbw) - dragged.offsetX;
          var my = event.clientY - bbox.top * ((can.height / pixelratio) / bbh) - dragged.offsetY;
          var point = myDiagram.transformViewToDoc(new go.Point(mx, my));
          myDiagram.startTransaction('new node');
          myDiagram.model.addNodeData({
            location: point,
            text: event.dataTransfer.getData('text'),
            color: "lightyellow"
          });
          myDiagram.commitTransaction('new node');

          // remove dragged element from its old location
          if (remove.checked) dragged.parentNode.removeChild(dragged);
        }

        // If we were using drag data, we could get it here, ie:
        // var data = event.dataTransfer.getData('text');
      }, false);

      // *********************************************************
      // Second, set up a GoJS Diagram
      // *********************************************************

      var $ = go.GraphObject.make;  // for conciseness in defining templates

      myDiagram = $(go.Diagram, "myDiagramDiv",  // create a Diagram for the DIV HTML element
        {
          "undoManager.isEnabled": true
        });
      window.PIXELRATIO = myDiagram.computePixelRatio(); // constant needed to determine mouse coordinates on the canvas

      // define a simple Node template
      myDiagram.nodeTemplate =
        $(go.Node, "Auto",
          { locationSpot: go.Spot.Center },
          new go.Binding('location'),
          $(go.Shape, "Rectangle",
            { fill: 'white' },
            // Shape.fill is bound to Node.data.color
            new go.Binding("fill", "color"),
            // this binding changes the Shape.fill when Node.isHighlighted changes value
            new go.Binding("fill", "isHighlighted", function(h, shape) {
              if (h) return "red";
              var c = shape.part.data.color;
              return c ? c : "white";
            }).ofObject()),  // binding source is Node.isHighlighted
          $(go.TextBlock,
            { margin: 3, font: "bold 16px sans-serif", width: 140, textAlign: 'center' },
            // TextBlock.text is bound to Node.data.key
            new go.Binding("text"))
        );

      // but use the default Link template, by not setting Diagram.linkTemplate

      // create the model data that will be represented by Nodes and Links
      myDiagram.model = new go.GraphLinksModel(
        [
          { text: "Alpha", color: "lightblue" },
          { text: "Beta", color: "orange" },
          { text: "Gamma", color: "lightgreen" },
          { text: "Delta", color: "pink" }
        ],
        []);
    }

  </script>
</head>
<body onload="init()">

<div id="sample">
  <div style="width: 100%; display: flex; justify-content: space-between">
    <div id="paletteZone" style="width: 160px; height: 400px; margin-right: 2px; background-color: lightblue; padding: 10px;">
      <div class="draggable" draggable="true">Water</div>
      <div class="draggable" draggable="true">Coffee</div>
      <div class="draggable" draggable="true">Tea</div>
    </div>
    <div id="myDiagramDiv" style="flex-grow: 1; height: 400px; border: solid 1px black"></div>
  </div>
  <input id="remove" type="checkbox" /><label for="remove">Remove HTML item after drag</label>
  <p>
  The "Palette" in this sample is not a Palette (or GoJS control) at all.
  It is a collection of HTML elements with draggable attributes using the
  <a href="https://developer.mozilla.org/en-US/docs/DragDrop/Drag_and_Drop">HTML Drag and Drop API</a>.
  </p>
  <p>
  This sample lets you drag these HTML elements onto the Diagram to create GoJS nodes.
  As the mouse passes over stationary nodes in the Diagram, they are highlighted.
  </p>
</div>
</body>
</html>